<?PHP if(!$form->isNew()){?>
<div class="sf_admin_form_row sf_admin_text sf_admin_form_field_created_by_user_id">
        <div>
      <span class="label_cont"><?php echo $form['created_by_user_id']->renderLabel();?></span>
      <div class="content ltr">
          <?php echo $form->getObject()->getCreator()?$form->getObject()->getCreator():__('N.A')?>
      </div>

          </div>
  </div>
<?php }?>